FRANKFURT, June 29 (Reuters) - BioNTech (22UAy.DE) and its U.S. partner OncoC4 Inc say they have started a late-stage study of their lung cancer immunotherapy candidate as the German COVID-19 vaccine maker seeks to advance its traditional focus on oncology drug development. The Phase III trial, which can potentially lead to a regulatory filing, will enrol about 600 patients, the companies said in a statement on Thursday. It will seek to show a benefit for people suffering from metastatic non-small cell lung cancer, which has progressed despite treatment with so-called checkpoint inhibitor drugs such as Merck & Co's (MRK.N) Keytruda. Earlier this month, a mid-stage trial showed that the drug candidate known as gotistobart shrunk tumours in close to 30% of study participants. https://www.reuters.com/business/healthcare-pharmaceuticals/biontech-oncoc4-start-late-stage-lung-cancer-drug-trial-2023-06-29/ https://www.cnbc.com/2023/06/05/moderna-cancer-vaccine-with-merck-keytr